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Date: Tuesday, May 10, 2011
Time: 6:00 PM to 8:00 PM
Place: Willow Tree Restaurant
6513 Regional St
Dublin, CA 94568
Speaker: Benjamin D. Santer
Program for Climate Model Diagnosis and Intercomparison
Lawrence Livermore National Laboratory
Title: How do we know that human activities have affected global climate?
About the meeting: Human-caused climate change is not a hypothetical future event. It is real, and we are experiencing it in our lifetimes. Despite compelling evidence of human effects on global climate, there is a continuing need for scientists to explain "how we know it's us". The first part of my talk will briefly summarize the scientific underpinning for "discernible human influence" conclusions of the Intergovernmental Panel on Climate Change. I will show that that the climate system is telling us an internally- and physically-consistent story. The message in this story is that observed changes in many different (and independently-measured) aspects of the climate system cannot be explained by natural causes alone.

Studies of the causes of climate change frequently rely on computer models of the climate system. Such models are the only tools we have for attempting to understand the size (and geographical and seasonal distribution) of the climate changes we are likely to experience over the 21st century. But not all computer models show equal skill in capturing key features of present-day climate. Should models with higher skill in reproducing today's climate be regarded as more trustworthy predictors of 21st century climate change? Is it easy to identify the "top 10" climate models in the world? How should decision-makers - and scientists interested in studying the impacts of climate change - use and interpret information on the strengths and weaknesses of different climate models? Can we find clever ways of reducing uncertainties in projections of future climate change? These are a few of the questions that will be addressed in the second part of the talk.

About the speaker: Benjamin David Santer

Dr. Benjamin Santer is an atmospheric scientist at Lawrence Livermore National Laboratory (LLNL). His research focuses on such topics as climate model evaluation, the use of statistical methods in climate science, and identification of natural and anthropogenic "fingerprints" in observed climate records. Dr. Santer's early research on the climatic effects of combined changes in greenhouse gases (GHGs) and sulfate aerosols contributed to the historic "discernible human influence" conclusion of the 1995 Report by the Intergovernmental Panel on Climate Change (IPCC). He spent much of the last decade addressing the contentious issue of whether model-simulated changes in tropospheric temperature are in accord with satellite-based temperature measurements. His recent work has attempted to identify anthropogenic fingerprints in a number of different climate variables, such as tropopause height, atmospheric water vapor, the temperature of the stratosphere and troposphere, and ocean surface temperatures in hurricane formation regions.

Dr. Santer holds a Ph.D. in Climatology from the University of East Anglia, England, where he studied under Professor Tom Wigley. After completion of his Ph.D. in 1987, he spent five years at the Max-Planck Institute for Meteorology in Germany, and worked with Professor Klaus Hasselmann on the development and application of climate fingerprinting methods. In 1992, Dr. Santer joined Professor Larry Gates at LLNL's Program for Climate Model Diagnosis and Intercomparison.

Dr. Santer served as convening lead author of the climate-change detection and attribution chapter of the 1995 IPCC report. More recently, he was the convening lead author of a key chapter of the U.S. Climate Change Science Program's report on "Temperature Trends in the Lower Atmosphere". His awards include the Norbert Gerbier-MUMM International Award (1998), a MacArthur Fellowship (1998), the U.S. Department of Energy's E.O. Lawrence Award (2002), and a Distinguished Scientist Fellowship from the U.S. Dept. of Energy, Office of Biological and Environmental Research (2005). He and his son Nicholas live in San Ramon, and enjoy rock-climbing and exploring California.

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